Patent GB-448521-A (GB)
Title: Control mechanism for use with web rolls
IPC: B65H23/06
Filed: 1935-01-04
Abstract: 448,521. Feeding webs. HOE & CO., Ltd., R., 109, Borough Road, London.-(Hoe & Co., Inc., R. ; 138th Street, New York, U.S.A.) Jan. 4, 1935, No. 350. [Class 100 (i)] A tensioning mechanism for a web fed to a printing-machine comprises a device adapted frictionally to engage the periphery of a web roll, a lever and weight device controlling the pressure applied by the frictional device to the web roll, a member such as a roller displaceable in dependence on the web tension, and means whereby the leverage of the lever and weight device is adjusted in dependence on the displacement of the roller so that the pressure on the web roll is varied in dependence on the tension of the web. An endless belt 14 which rests upon the periphery of the active roll 12 is mounted upon rollers 15 carried in a support comprising a pair of arms 17 keyed to a rockshaft 18. A weight supporting member 22 fixed to the shaft 18 comprises an arm 38 with two lugs 39 supporting a rod 41 along which is slidably mounted a weight 42, which acts as a counter-weight for the belt supporting means. The web passes over a floating roller 45 mounted in bearings which slide in guideways 49 and to which are attached the ends of two chains 59 which pass round sprockets 52, 55, the latter of which are carried by arms attached to a shaft 56 to which is secured an arm 62 adapted to engage adjusting screws 64 whereby the shaft 56 may be rotated to take up the slack of the chains 59. One of a pair of blocks 66 attached adjustably to the chains 59 carries a rod 68 pivotally attached to the weight 42 and a weight 77 carried by a cable 76 which passes round a spiral groove in a conical pulley 74 is provided to bias the roller 45 against the web in such a way that as the loop in the web is diminished the effective pull of the weight is increased. The belt 14 is driven from gearing from a driven shaft 27 at a speed slightly slower than the speed of the running web and, in order to take up slack as the diameter of the roll decreases, a compensating roller 28 is provided which is carried by arms 31 secured to a rock shaft 32 to which is also fixed a lever 34 having an adjustable weight 36 mounted thereon. In operation as the tension of the web varies, the position of the roller 45 changes and moves the chains 59; the consequential movement of the rod 68 and of the counter-weight 42 causes the belt 14 to be applied more or less strongly to the roll. In the modification shown in Fig. 8, the belt 14 is driven from the main drive-shaft through a shaft 85 to which is fixed a roller 93 round which the belt passes, and is tensioned by a roller 94 which is mounted in the spring-pressed arms 96. Freely mounted wheels 102 prevent the belt engaging the web roll as it passes round the lower guide pulley 92. The belt supporting arms 84 are freely pivoted upon the shaft 85 and the pressure is varied according to the tension of the web under the control of a floating roller 117, which is mounted in arms 116 fixed to a shaft 113. A counter-weight roller 110 for the belt supporting means is carried by arms 115 pivotally attached to levers 112 also fixed to the shaft 113 and the counter weight runs on rails 105 carried by pivoting arms 103 to which are also attached links 107 connected at their lower ends to the belt supporting members. Two further counterweights 119 mounted on rods 120 fixed to the shaft 113 partially counter-balance the weight of the arms 116 and the floating roller 117 and an adjustable spring 123 serves to bias the floating roller and produce a downward pressure of the'roller on the web. By this means any change in the position of the floating roller 117 rocks the shaft 113 and moves the roller 110 along the rails 105. The consequential change in the downward force due to the roller 110 causes the arms 103 to rotate about their pivot and moves the links 107 and thereby the belt supporting members to apply the belt with more or less force to the roll. The distance between the shaft 85 about which the belt supporting means pivot and the connection to such means of the links 107 is made greater than the distance between the upper end of the links 107 and the pivotal support 104 of the levers 103 ; thus providing a reduction linkage which permits the use of a slight operating force to rock the belt supporting means. Rollers 127 on the arms 116 carrying the floating roller 117 and fixed stops 126 prevent excessive movement in the event of a break in the web. Means is also provided to maintain constant the tension per unit length of paper when rolls of less than full length are employed. The compensating means employed comprises a yoke 128 pivotally mounted on a shaft 129 and carrying between the ears of the voke a screw 130 which can be rotated to vary the position of a weight 134 carried by the yoke. The short end of the yoke is connected to a belt-support actuating link 107 so as to be moved when the link is moved, a suitable clearance slot 136 for the connecting stud 135 being provided to permit the yoke to rock about its shaft 129. By adjusting the position of the weight 134 it will exert a greater or less effect on the link 107 and therefore on the belt supporting means with a consequential effect on the belt pressure.